An energy and cytosol-dependent cell-free system consisting of liver nuclei in surrogate cytoplasm has now been shown for the first time to support the processing and transport of fully functional mRNA and rRNA (as the corresponding RNP and in a regulated manner). We now propose to utilize this system to characterize (particularly with respect to specificity, heterogeneity and mechanism and sites of action) the cytosolic transport factors. By comparing the homologous and heterologous cell-free systems derived from liver and brain an assessment can be made of the contribution of nuclei and cytosol to regulation at this post-transcriptional level. A second form of regulation residing in hormone receptors in the nuclear membrane and nuclear hnRNP has been identified and will be rigorously characterized. The transport of rRNA will be monitored by standard procedures utilizing gradient or gel fractionation, while mRNA transport will be monitored via translation products synthesized in response to the mRNA or by cDNA made to total sequences or to specific sequences (i.e., albumin and alpha 2u-globulin). The cDNA will be invaluable in determining whether potential regulators affect nuclear processing or nucleocytosol transport.